In certain situations it may be advantageous to extend the radio coverage of a cellular telecommunication system by using a wireless relay node, which is connected to a base station. The relay node may constitute one or more cells of its own, or may be used to extend the cells covered by the base station.
In e-UTRAN (Evolved Universal Terrestrial Radio Access Network), also known as LTE, self-backhauling is one of the relaying techniques which are considered to be included in the radio access network standard. The concept of self-backhauling implies that a wireless base station is wirelessly connected to the remaining part of a network via another cell, sometimes called the anchor cell, here referred to as the donor cell. The donor cell is controlled by an eNB (evolved Node B), which here will be referred to as the donor eNB or donor node. The donor eNB may also be called the anchor eNB. The wireless eNB will here be referred to as the relay node (RN) or relay. The relay may also be called the self-backhauled eNB or the s-eNB.
The use of wireless backhaul to a base station by means of, for example, a specific radio-link technology such as MiniLink, sometimes also called micro wave, has been used for many years. These specific technologies may, however, require additional transceiver equipment or specific, dedicated frequency bands to operate in, and may also require line-of-sight conditions.
The concept of self-backhauling also implies that the link between the donor eNB and the relay node, here referred to as the self-backhaul link, should be possible to operate in the same frequency spectrum, i.e. frequency-overlapped with, the radio access links that provide access for mobile terminals, also known as User Equipment (UEs), within the donor cell and the UEs within the cell(s) controlled by the relay node. It is also typically assumed that the radio technology used for the self-backhaul link is basically similar to the one used within the donor cell and the cell(s) of the relay node respectively, possibly with some additional extensions to optimize for the backhaul application. For example, in case the donor eNB and the relay node use the LTE radio access technology for communicating with UEs within their cell(s), the self-backhaul link should also be LTE-based, or at least based on an LTE-like radio technology. Signals which overlap in frequency interfere with each other, which may obstruct reception of the signals.